In recent years, an organic transistor having an active layer made from an organic compound has been actively developed. In a manufacturing process for the organic transistor, for example, as disclosed in Patent document 1, the active layer is formed by a deposition method such as an OVPD (Organic Vapor Phase Deposition) method.
Meanwhile, an organic compound is attached to the inside of a processing chamber after depositing in a deposition apparatus used for forming the active layer. Mixing the attached organic compound into the active layer as an impurity may brings characteristic deterioration of a transistor. Therefore, it is required to develop technique by which an active layer with high purity can be formed.    Patent document 1: “Self-Organized Organic Thin-film Transistor for Flexible Active-Matrix Display”, Sung Hwam Kim et al., SID 04 DIGEST, pp. 1294-1297